Exoplanets/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim and Moby are sitting on their living room sofa, watching television. On TV, an alien and a robot emerge from a flying saucer. The robot shoots two humans with a death ray from its eyes. The humans turn into skeletons and fall to the ground with a rattling sound. Moby claps. Tim looks at Moby and forces a laugh. TIM: Heh-heh. Huh. Tim reads from a typed letter. TIM: Dear Tim and Moby, Are there humans living on any other planets? From, Horvath. Earth is the only planet we know of with life on it. An animation shows the planets in our solar system. A large arrow points at the third planet from the sun, Earth. TIM: Scientists are still searching for signs of any type of extraterrestrial life in our solar system, even just tiny creatures like microbes. But as far as we know, neither the seven other planets nor the hundreds of moons in our solar system are well-suited to complex life. An animation takes the viewer away from the sun, passing each of our solar system's planets. MOBY: Beep. TIM: You know, big things like plants and animals. An animation shows a woman, zebra, snake, bird, and fox, along with different types of plants. TIM: For one thing, large organisms can't exist in places where it's too hot, like on Venus, or where it's too cold, like on Pluto, or anywhere where there's no liquid water, like on our moon. Side-by-side animations show a porcupine on Venus, where the porcupine burns up. The next animation shows a porcupine on Pluto, where it freezes solid. The third animation shows the porcupine on the moon, with Earth in the background. The porcupine is panting for water. TIM: That's one of the reasons astronomers are looking for planets outside of our solar system, and they've found them. They're called extrasolar planets, or exoplanets. An animation shows a faraway group of exoplanets. MOBY: Beep. TIM: Oh, yeah. We've been able to detect exoplanets since the early 1990s. They're hard to find, because planets are pretty dim compared to their stars. An image shows a large, white star with a gassy halo. In that halo is a dim planet, pointed out by an arrow. TIM: We're able to see many of the planets of our solar system without using a telescope, but that's mostly because they're pretty close by. Planets reflect light from the sun, making them look like stars in the night sky. An animation shows a brown, cloudy planet, which Moby can see in the night sky through the window. TIM: But any light reflecting off planets around other stars is drowned out by light from the star itself. An animation shows a planet orbiting a large, white, gassy star. TIM: Even with a powerful telescope, the nearest stars are still so far away that their visible light overwhelms the light reflected off any possible planets. An animation shows a star as one of several in the night sky. Its planet can no longer be seen. Then those stars appear through the round lens of a telescope. The planet is still invisible. TIM: It's like trying to see a lightning bug flying in front of a spotlight. An animation shows a yellow lightning bug flying erratically in front of a white spotlight. When the bug is directly in front of the spotlight, it can't be seen at all. MOBY: Beep. TIM: Well, there are a bunch of different ways that astronomers can detect the presence of exoplanets indirectly. Two of these methods measure when a planet's gravity gives a small tug on the star that it's orbiting. An animation appears of a planet quickly orbiting a star. The star moves back and forth as the planet's gravity pulls on it. TIM: In astrometry, the wobbling star's position is checked against what we know about where it's supposed to be in the night sky. An animation shows a scientist looking at a group of stars on a large screen. The words "theoretical positions" and "actual positions" are shown as a program measures the offset of a star. TIM: But distortions caused by Earth's atmosphere can make this technique kind of unreliable. An animation shows a star's light bending as it goes through Earth's atmosphere on its way to an observatory. Through a telescope lens, it looks like it's wobbling. TIM: The radial velocity method, or Doppler method, has had more success in detecting the wobble effect. The animation of the planet orbiting a wobbly star reappears. TIM: It measures the shift in speed of a star wobbling toward and away from Earth. The Doppler method has been used to find more exoplanets than any other. An animation shows radio waves passing between Earth and a wobbling star. A monitor is reporting the changing speed of the star's wobble. MOBY: Beep. TIM: Another common way to detect exoplanets is photometry, which detects tiny changes in the intensity of starlight. The idea is that if an exoplanet gets between the Earth and the star it's orbiting, the star will get momentarily dimmer by a very small amount. Photometry is exciting because it can detect planets the same size as Earth and even give us information about the planet's atmosphere. An animation shows Earth and a wobbling star with its orbiting planet. Another animation shows the star dimming slightly as the planet passes in front of the star. TIM: The gravitational methods tend to find large planets, since their strong gravity makes stars wobble so much more obviously. An animation shows a large, ringed planet orbiting a star. MOBY: Beep. TIM: Actually, astronomers have directed a few exoplanets directly. Using special telescopes that detect infrared radiation, they were able to measure the planets' temperatures. They could even create an image of the planets with the infrared data. An image shows an infrared image of a star and planet. TIM: It's pretty exciting when you think about it. The existence of extrasolar planets proves that our solar system is not a unique phenomenon in the universe. If our solar system isn't unique, that means there are probably billions of planets out there. An animation shows the Milky Way, which is a spiral galaxy. TIM: And if that's true, odds are that there's life on some of those planets just waiting to make contact. A silhouette shows a six-armed, pointy-headed humanoid creature, standing in an alien landscape. Ominous music plays, and lightning flashes through purple skies. As the silhouette approaches, its bizarre features can be seen. There is a knock at the door. TIM: Aah! Tim and Moby jump with fright. MOBY: Beep. TIM: Oh, I think it's, I think it's just the pizza guy. Category:BrainPOP Transcripts